THE HUMAN BODY AND ITS CONSTRUCTION Let us now look briefly at the construction of the human body and the duties which its various parts are intended to perform, after which we will take note of the methods of preserving health in general, and the diseases and injuries which must be guarded against. First, some explanations of the terms used in these connections: We divide all nature into three classes of objects, those belonging to the Animal, Vegetable and Mineral Kingdoms, and all things belong in one or another of these. They are also divided into organic and inorganic bodies. The first are those having organs by which they grow, such as animals and plants. Inorganic bodies are those which are without life of their own, such as air, water, stone and the like. All inorganic bodies are included in the mineral kingdom. Those organic bodies which have no power to feel are included in the vegetable kingdom, and those which have the power to feel form the animal kingdom. There are things in nature which are so close to this dividing line that even scientists disagree as to whether they belong to the vegetable or animal kingdom. The parts of an organized body, such as the mouth or the foot of an animal, the root or the leaf of a plant, are called the organs, and the work which an organ is intended to perform is called its function. The material out of which any organ is composed is called tissue, and in the human body, for instance, at least six different kinds of tissue are found, forming the various organs. We will speak of the various solids and fluids of the body by name, only in connection with their ailments and their care hereafter. The tissues themselves are composed of fifteen of the sixty-five chemical elements, or simple substances, known to exist in nature. The various organs of similar structure and common purpose found in the human body, when taken together, are called a system. These are the Osseous System, the Muscular System, the Digestive System, the Circulatory System, the Respiratory System and the Nervous System. The Osseous System means the skeleton, which gives shape to the body and supports it, enables us to move and extend our limbs, and protects the delicate organs from injury. The Muscular System is the flesh of the body, forming a pad or covering around the bones, and thus also serving as a protection, in addition to producing at will the motions of our limbs and the controllable organs. The Digestive System is composed of those organs which receive, transmit and dispose of our food, separating the waste matter from the useful, and giving the latter to our nourishment and strength. The mouth, the stomach, the intestines, and various other organs are included in this service.